Dabs put the magazine into the gun then walked over to a large grey metal water tank about three feet wide, ten feet long and three feet high. Jane followed him.

‘We need to test-fire the gun. Friction from passing through the water slows the bullets down and they end up on the bottom of the tank in good condition to examine them on a comparison microscope.’ He held the pistol out to her. ‘Do you want to fire it?’

‘No thanks, I’ll leave that to you,’ she said, worried something might go wrong if she fired it.

Dabs placed the muzzle of the pistol in an open tube at the end of the tank and fired three rounds, which he then removed from the water using a soft rubber grabber, so as not to make any scratch marks on the bullets. Wearing soft white cloth gloves he delicately dried the bullets with non-abrasive tissue paper, took one and placed it on one of two microscopes mounted side by side and connected by an optical bridge. He then removed three small tagged cardboard exhibit boxes from the pistol case, which Jane knew were used to store bullets fired at crime scenes. He opened a box with a tag marked Daily Express Robbery 1976, removed a slightly damaged-looking bullet and placed it on the other microscope and started to look for any similarities in the striation marks between the two bullets. Dabs took his time comparing the two bullets while making notes, and nearly five minutes had elapsed when Elliott walked in.

‘How’s it going?’ he asked Dabs, who looked up from the microscope.

‘Bloody hell, you were right. The bullet I just test-fired is a match to the one recovered from the Daily Express robbery.’

Elliott looked cautiously pleased. ‘Are you sure?’

‘Take a look for yourself. I’ve got the groove marks lined up perfectly.’

Elliott spent a minute looking at the two bullets in the microscope. ‘That’s brilliant work, Dabs. What about the bullets from the other two robberies?’

‘I’m just about to check them. It’ll take me ten or fifteen minutes. If you want a coffee while I do it, my office is down the corridor.’

Jane went with Elliott to Dabs’s office. She flicked the kettle on.

‘If the gun Dabs just test-fired was lawfully seized in 1976 by Murphy and matches to a bullet recovered back then, I don’t see how that’s evidence of corruption.’